Bags and carrying cases are commonly used to transport items from one location to another. Items may be contained and supported within an internal enclosure during transportation. Most bags also include some form of user attachment system that allows a user to support the bag during transportation. Many types of user attachment systems are designed to be positioned on a user's body in a configuration that both supports the bag but does not require the use of appendages. For example, backpack shoulder straps may be individually looped around each of a user's shoulders to support the backpack in an orientation that does not require the user to hold the backpack in place with their arms. However, each type of user-attachment system possesses particular performance characteristics and limitations that affect the utility of the bag. For example, a single shoulder strap or messenger-style user attachment system is undesirable for exclusive support of a bag with loads of higher weight due to discomfort.
Bags and carrying cases may be further classified according to their overall shape, user-attachment system(s), and material of composition. One subset of carrying cases or bags includes a set of two shoulder straps for individually and simultaneously attaching around both of a user's shoulders. This form of bag is commonly referred to as a backpack. A backpack may also include other user-attachment systems in addition to the shoulder straps, such as waist belts, handles, single shoulder straps, etc. The enclosure portion of a backpack is primarily positioned on the dorsal torso region of the user, and the dual shoulder attachment system includes two straps that circumscribe the ventral side of the shoulders. Therefore, each of the straps encircle one of the user's shoulders respectively. The two shoulder straps are generally adjustable in length to accommodate different user torso shapes. The simultaneous encircling of a user's shoulders transfers the weight of the backpack contents or load to the user's shoulder region without requiring the user to support the enclosure portion in any manner with their hands or lower arms.
One of the problems with existing dual shoulder strap systems is the inability to effectively accommodate for opposing shoulder movements which occur during ambulation and/or incidental torso articulation. For example, when a user laterally leans to one side, the opposing shoulder is naturally raised with respect to the leaning shoulder. Conventional dual shoulder strap systems are rigidly individually coupled to the backpack; therefore, in circumstances such as the one described above, the straps force the user to perform additional work associated with muscular accommodation for the backpack load being tilted in a manner that matches the torso of the user. Over the course of extended use, a user may be forced to perform significant unnecessary work as a result of natural shoulder movements or leaning. In addition, conventional rigid individual coupling of shoulder straps with a heavy backpack load causes instability to the user in certain circumstances.
Therefore, there is a need in the industry for an efficient backpack dual shoulder strap system that accommodates for opposing shoulder articulation while maintaining optimal weight and cost parameters.